KYTL 5.2

Igneous Rocks

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Vocabulary

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Extrusive rock- a igneous rock that forms from lava
Intrusive rock- a igneous rock that forms form magma
Porphyritic texture- a rock with large crystals on a background of much smaller crystals

Outline

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Characteristics of Igneous Rocks

• Origin
  • extrusive rock- forms from lava
  • intrusive rock= forms from magma
  • intrusive rock forms beneath the surface
  • extrusive rock forms above the surface
  • basalt
    • forms much of crust
    • forms from lava
    • extrusive
  • granite
    • most abundant intrusive rock in continental crust
    • forms the core of many mountain ranges
• Texture
  • texture depend on size/shape
  • fine-grained
    • lava cools rapidly (small crystals)
    • coarse-grained
      • slow cooling (large crystals)
    • porphyritic
      • forms when intrusive rocks cool in 2 stages
      • magma starts cooling (large crystals)
• Mineral Composition
  • igneous rocks low in silica-dark colored
  • igneous rocks high in silica-light colored

Uses of Igneous Rocks

• used for
  • tools
  • building material
  • statues
  • stonework
  • curbstones
  • floors
• why?
  • hard
  • dense
  • durable
• basalt
  • gravel for construction
• pumice
  • cleaning and polishing
• perlite
  • soil mixes